[PATCH 6/9] drm/tegra: gem: Add a clarifying comment

Thierry Reding
2021-03-23T15:55:11Z

From: Thierry Reding <treding@nvidia.com>

Clarify when a fixed IOV address can be used and when a buffer has to
be mapped before the IOVA can be used.

Signed-off-by: Thierry Reding <treding@nvidia.com>
---
drivers/gpu/drm/tegra/plane.c | 8 ++++++++
1 file changed, 8 insertions(+)

diff --git a/drivers/gpu/drm/tegra/plane.c b/drivers/gpu/drm/tegra/plane.c
index 19e8847a164b..793da5d675d2 100644
--- a/drivers/gpu/drm/tegra/plane.c
+++ b/drivers/gpu/drm/tegra/plane.c
@@ -119,6 +119,14 @@ static int tegra_dc_pin(struct tegra_dc *dc, struct tegra_plane_state *state)
dma_addr_t phys_addr, *phys;
struct sg_table *sgt;

+ /*
+ * If we're not attached to a domain, we already stored the
+ * physical address when the buffer was allocated. If we're
+ * part of a group that's shared between all display
+ * controllers, we've also already mapped the framebuffer
+ * through the SMMU. In both cases we can short-circuit the
+ * code below and retrieve the stored IOV address.
+ */
if (!domain || dc->client.group)
phys = &phys_addr;
else
--
2.30.2